The present invention relates to an improved groove pattern for the friction facings of wet clutches.
Prior known clutch facings for wet clutches had a variety of groove patterns formed in the facing, the most common being the waffle pattern, such as shown in U.S. Pat. No. 4,280,609. In the waffle pattern, a series of parallel grooves intersect at right angles to a second series of parallel grooves. The oil or other cooling fluid for the wet clutch passes through the groove pattern from the inner edge to the outer edge of the friction facing under the impetus of centrifugal force.
Other types of conventional grooving patterns are shown in FIGS. 8 through 11 of U.S. Pat. No. 2,927,673. The typical waffle grooving pattern is shown in FIG. 7 of this patent, while a circumferential grooving pattern is shown in FIG. 8. FIG. 9 discloses a waffle pattern with curved grooves, FIG. 10 discloses straight grooves in an angled pattern, and FIG. 11 discloses radial grooves. Another known groove pattern is a single lead spiral groove pattern.
However all of the above groove patterns has the major disadvantage of a substantial temperature gradient across the width of the friction facing. The equilibrium temperature for the wet clutch facing is not uniform with the highest temperature occurring adjacent the outside diameter of the facing, and thus limits the thermal capacity of the clutch; while the capacity of a substantial portion of the clutch facing is underutilized. The present invention overcomes the disadvantages of prior known wet clutch face grooving patterns.